Both potatoes and tomatoes can quickly be defoliated by Phytophthora infestans, an oomycete active in wet cool conditions. In North Carolina disease damage occurs from June through the end of the season.

Potato late blight
image by Howard F. Schwartz –bugwood

Management Strategies:

• Grow varieties known to be resistant to Potato late blight
• Use disease free seed potatoes
• Plant early to avoid disease
• Limit leaf wetness (water the soil, not the leaves, use drip irrigation, space plants to allow air circulations)
• Remove and discard infected plants

More information and images.